Process of refining vegetable and animal oils



Nov. 28, 1939.\

O. E. FRDING Filed Sept. 2. '1957 iff/744555.'

CE/vr/e/Faaf PROCESS 0F REFINING VEGETABLE AND ANIMAL OILS ozoffzmgffahjPatented Nov. 28, 1939 UNITED sTATEs PATENT OFFICE PROCESS OF REFININGVEGETABLE AND ANIMAL OILS Application september 2, 1937, serial No.162,100

In Sweden October 8, 1936 '3 Claims.

In the refiningof vegetable oils containing free fatty acids it is knownto intimately mix the oil with a saponifying agent, usually an alkalisuch as caustic soda, to effect a saponification of the fatty acids andto then separate the oil from the soaps by settlement or centrifugation.It is necessary to heat the oil to temperatures which Vary with theduration of the process and the character of theoil being treated. Theoil is sometimes heated to thedesired ultimate temperature before mixingwith the alkali, sometimes during mixing, sometimes after mixing, andsom'etimes during and after mixing, and it is sometimes/heated beforemixing to a moderate temperature and during or after mixing to the naltemperature desired. When the heating is wholly or mainly effected inthe mixer, it is usual to ldecrease the rate or amount of agitation asthe heating of the oil proceeds so that the oil will be in acomparatively quiescent state before separation. proposed or practicedboth in batch and continuously. Centrifugal separation of the oil andthe soap is of advantage in that the time of heating and mixing may besomewhat shortened and the mixture conveyed to the centrifuge beforesaponification of the fatty acids is quite completed, the saponicationbeing completed in the separator due to the -intimate admixture thereinof the constituents before their separation is completed. In all theseprocesses it is customary, after the separation, whether bycentrifugation or settling, to wash with water and separate thesoap-containing water from the oil.

It has been. proposed `to heat the oil to various maximum temperatures,ranging from 80 F. to 140 or 150 F. or even higher. The objection to thehigher range of temperature is that the soaps are'more soluble in theoil at a higher temperature and soap contained in the oil in solutioncannot of course be separated by gravity or centrifugal force. In thesubsequent washing part of the soap is hydrolyzed and the fatty acidsthereby liberated are dissolved in the oil, so that the ultimate refinedoil does not in Vmany cases vmeet the requirement of neutrality. Theobjections to heating the oil to a relatively high temperature may be,of course, avoided by not heating the oil during the process or byheating it to within a comparatively low temperature range;

`but this method is objectionable in that the neu- 'Ihese variousprocesses have been A bleaching of the` I have found that the advantagesof both high and low heating may be securedand the disadvantages of bothavoided, by interposing, between the mixing and heating step or stepsand the centrifuging step, a cooling step whereby the temperature, priorto separation; is so reduced as to throw out of solution a majorproportion of the soaps. In many cases,4by the use of this process,separated oil is of such quality Athat the subsequent Washing operationmay be altogether dispensed with, which is obviously an additionaladvantage.

The process is applicable to any of the known processes, but itisparticularly applicable to any of the known processes that is practicedcontinuously as distinguished from batch processes.

The single figure of the drawing illustrates in diagram an apparatusvadapted to carry out the process in a continuous manner.

'I'he diagrammed apparatus illustrates a known continuous apparatus forpracticing the process continuously with the addition thereto of acooler interposed in the series of devices just before the outlet to thefirst separator. The crude oil from tank I (which may or may not bepreliminarily heated to a comparatively low temperature) flows or may bepumped through the tube 2 into and through the mixer 4. Into tube 2 asolution of caustic soda, sodium or potassium carbonate, or any othersuitable alkali or saponifying agent, is introduced from the tank 3. Anysuitable proportioning device adapted to insure a uniform ratio betweenthe oil feed and the alkali feed may be utilized, but the use of suchdevices is Well known and forms no part of the invention and I havemerely shown two Valves, Il and l2, on pipe 2 y and on the pipe fromtank 3, which may be handregulated to govern the proportioning. Thereaction starts in the v`mixer and may be completed in the heater 5; orall the heating may be applied in the tank I; or the relative positionsof the mixer and heater may be reversed; or some or all of the heatingmay be effected in the mixer, which for that purpose may be steamjacketed, as indicated by the reference numeral 13. From the heater 5the oil passes through a cooler 6 and thence goes tothe centrifugalseparator 1. If the separated oil still contains too much soap to meetthe requirements in any given case, the oil, by means of pump 8, isconveyed to a water Washer 9 and thence to a centrifugal separator I0,wherein the soap-containingA water is separated from the oil.

In treating .some oils it is advantageous to mix with alkali at a ratherlow temperature, since lit cluding the cooler.

avoids the formation, in the rst part of the process, of a less readilyseparable emulsion. With most oils, of which cocoa oil and cottonseedoil are examples, the emulsion is less pronounced and it is 4usuallyentirely practicable to do all Vthe heating in the tank I, say by meansof a steam coil I3; or the positions of the heater 5 and mixer 4 may bereversed so that the oil will be heated in stream before ygoing to themixer. I n treating practically all oils it is quite feasible to effectthe heating simultaneously with the mixing.

When refining a peanut oil containing 3.5% free fatty acids (in theapparatus shown, with the cooler 6 omitted) with a 15% NaOH solution,

` drolysis.

The same oil was treated according to the present invention in theapparatus shown, in-

The mixing was carried out at about 78 F., the .oil was heated to about122 F. and cooled to about 86 F. prior to separation. The content ofNaOH in the separated oil was .01%. The content of fatty acids in thewashed oil was .10%.

A soya oil containing 1.8% free fatty acids was mixed with a 10% NaOHsolution at about 68 F. and was separated at about 113 F. The NaOHcontent in the separated oil was .03%, free fatty acids .07%. Afterwashing the content of free fatty acids was .12%.

The same oil was treated according to the present invention in theapparatus shown, including the cooler, but was cooled to about 68 F.before the separation.` The NaOH content in the separated oil was .002%,and since this corresponds to a content of soap of only about .015%, theoil could be treated with bleaching earth without Washing.

A cocoa oil having a content of fatty acids of 5.4% was mixed with a 1%NaOH solution at about 112 F. and was` separated at about 140 F. TheNaOH content of the separated oil was .04%, the content of free fattyacids .08%. After wash,-l ing the content of free fatty acids was .16%.

'I'he same oil was treated in accordance with my invention,lthe heating,however, being effected in the tank I instead of in the heater 5. 'I'hetemperature of the oil when being mixed with the lye wasv about 122 F.and at the separation was about 90 F. The NaOH content of the separatedoil was .009%, after the washing .002%. 'I'he content of fatty acids inthe washed oil was .09%.

What I claim and. desire to protect by Lettersl Patent is:

1. In the process of refining vegetable and animal oils wherein the oilis mixed with a saponifying agent to effect sapon'ification of fattyacids contained in the oil and heated through a considerable range oftemperature and the oil then separated from undissolved soaps, theimprovement which comprises interposing between they mixing and heatingprocedure and the separation of the oil from the soaps a cooling step inwhich the mixture is cooled through the major part of the temperaturerange through which it was heated to thereby increase the proportion' ofundissolved soaps before separation and substantially reduce theproportion of soaps inthe subsequently separated oil.

2. In the continuous process of refining vegetable and animal oils,which comprises, as a first procedure, flowing a stream of a saponifyingagent into contact with a, owing stream of oil,

subjecting the mixture during its flow to a mixing action so as toeifect saponication of fatty acids in the oil and heating the oil towithin a range of temperature customary in the process, and then as afollowing procedure subjecting the flowing mixture to centrifugal forceand thereby separating the oil from the soaps that are not dissolved inthe oil, the improvement which comprises eiecting a substantialreduction inthe soap content of the separated oil by reducing thetemperature of the oil between the mixing and heating procedure and thecentrifugal separation procedure to a temperature substantially nearerto that of the unheated oil than to that to which the oil was previouslyheated.

3. In the continuous process of refining vegetable and animal oils,which comprises, as a first procedure, flowing a stream of a saponifyingagent into contact with a flowing stream of oil, subjecting the mixtureduring its flow to a mixing action so as to eifect saponiiication offatty acids in the oil and heating the oil to Within a range oftemperature customary in the process, then as a following proceduresubjecting the flowing mixture to centrifugal force to thereby separatethe oil from the soaps not dissolved therein, and then as a finalprocedure washing the separated oil with water and separating thesoap-containing Water from the oil, the 11nprovement which compriseseffecting a substantial reduction in the fatty acid content of the finalwashed oil by reducing the temperature of the oil between the mixing andheating procedure and the centrifugal separation procedure through themajor part of the temperature range through which it was heated.

-oLoF EINAR. FRDINGf

